[C++11] Add range based accessors for the Use-Def chain of a Value.

This requires a number of steps.
1) Move value_use_iterator into the Value class as an implementation
   detail
2) Change it to actually be a *Use* iterator rather than a *User*
   iterator.
3) Add an adaptor which is a User iterator that always looks through the
   Use to the User.
4) Wrap these in Value::use_iterator and Value::user_iterator typedefs.
5) Add the range adaptors as Value::uses() and Value::users().
6) Update *all* of the callers to correctly distinguish between whether
   they wanted a use_iterator (and to explicitly dig out the User when
   needed), or a user_iterator which makes the Use itself totally
   opaque.

Because #6 requires churning essentially everything that walked the
Use-Def chains, I went ahead and added all of the range adaptors and
switched them to range-based loops where appropriate. Also because the
renaming requires at least churning every line of code, it didn't make
any sense to split these up into multiple commits -- all of which would
touch all of the same lies of code.

The result is still not quite optimal. The Value::use_iterator is a nice
regular iterator, but Value::user_iterator is an iterator over User*s
rather than over the User objects themselves. As a consequence, it fits
a bit awkwardly into the range-based world and it has the weird
extra-dereferencing 'operator->' that so many of our iterators have.
I think this could be fixed by providing something which transforms
a range of T&s into a range of T*s, but that *can* be separated into
another patch, and it isn't yet 100% clear whether this is the right
move.

However, this change gets us most of the benefit and cleans up
a substantial amount of code around Use and User. =]

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@203364 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 22 insertions, 31 deletions

diff --git a/lib/Target/NVPTX/NVPTXAsmPrinter.cpp b/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
index 8e2cf82224..25108bc39a 100644
--- a/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
+++ b/lib/Target/NVPTX/NVPTXAsmPrinter.cpp
@@ -699,12 +699,11 @@ static bool usedInGlobalVarDef(const Constant *C) {
     return true;
   }
 
-  for (Value::const_use_iterator ui = C->use_begin(), ue = C->use_end();
-       ui != ue; ++ui) {
-    const Constant *C = dyn_cast<Constant>(*ui);
-    if (usedInGlobalVarDef(C))
-      return true;
-  }
+  for (const User *U : C->users())
+    if (const Constant *C = dyn_cast<Constant>(U))
+      if (usedInGlobalVarDef(C))
+        return true;
+
   return false;
 }
 
@@ -730,11 +729,10 @@ static bool usedInOneFunc(const User *U, Function const *&oneFunc) {
                           (md->getName().str() == "llvm.dbg.sp")))
       return true;
 
-  for (User::const_use_iterator ui = U->use_begin(), ue = U->use_end();
-       ui != ue; ++ui) {
-    if (usedInOneFunc(*ui, oneFunc) == false)
+  for (const User *UU : U->users())
+    if (usedInOneFunc(UU, oneFunc) == false)
       return false;
-  }
+
   return true;
 }
 
@@ -765,12 +763,11 @@ static bool canDemoteGlobalVar(const GlobalVariable *gv, Function const *&f) {
 
 static bool useFuncSeen(const Constant *C,
                         llvm::DenseMap<const Function *, bool> &seenMap) {
-  for (Value::const_use_iterator ui = C->use_begin(), ue = C->use_end();
-       ui != ue; ++ui) {
-    if (const Constant *cu = dyn_cast<Constant>(*ui)) {
+  for (const User *U : C->users()) {
+    if (const Constant *cu = dyn_cast<Constant>(U)) {
       if (useFuncSeen(cu, seenMap))
         return true;
-    } else if (const Instruction *I = dyn_cast<Instruction>(*ui)) {
+    } else if (const Instruction *I = dyn_cast<Instruction>(U)) {
       const BasicBlock *bb = I->getParent();
       if (!bb)
         continue;
@@ -797,10 +794,8 @@ void NVPTXAsmPrinter::emitDeclarations(const Module &M, raw_ostream &O) {
       emitDeclaration(F, O);
       continue;
     }
-    for (Value::const_use_iterator iter = F->use_begin(),
-                                   iterEnd = F->use_end();
-         iter != iterEnd; ++iter) {
-      if (const Constant *C = dyn_cast<Constant>(*iter)) {
+    for (const User *U : F->users()) {
+      if (const Constant *C = dyn_cast<Constant>(U)) {
         if (usedInGlobalVarDef(C)) {
           // The use is in the initialization of a global variable
           // that is a function pointer, so print a declaration
@@ -816,9 +811,9 @@ void NVPTXAsmPrinter::emitDeclarations(const Module &M, raw_ostream &O) {
         }
       }
 
-      if (!isa<Instruction>(*iter))
+      if (!isa<Instruction>(U))
         continue;
-      const Instruction *instr = cast<Instruction>(*iter);
+      const Instruction *instr = cast<Instruction>(U);
       const BasicBlock *bb = instr->getParent();
       if (!bb)
         continue;
diff --git a/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp b/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
index 860d939357..45f0734c16 100644
--- a/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
+++ b/lib/Target/NVPTX/NVPTXGenericToNVVM.cpp
@@ -146,10 +146,8 @@ bool GenericToNVVM::runOnModule(Module &M) {
     // variable initializers, as other uses have been already been removed
     // while walking through the instructions in function definitions.
     for (Value::use_iterator UI = GV->use_begin(), UE = GV->use_end();
-         UI != UE;) {
-      Use &U = (UI++).getUse();
-      U.set(BitCastNewGV);
-    }
+         UI != UE;)
+      (UI++)->set(BitCastNewGV);
     std::string Name = GV->getName();
     GV->removeDeadConstantUsers();
     GV->eraseFromParent();
diff --git a/lib/Target/NVPTX/NVPTXLowerAggrCopies.cpp b/lib/Target/NVPTX/NVPTXLowerAggrCopies.cpp
index 7385e8f39a..f0c3663551 100644
--- a/lib/Target/NVPTX/NVPTXLowerAggrCopies.cpp
+++ b/lib/Target/NVPTX/NVPTXLowerAggrCopies.cpp
@@ -123,7 +123,7 @@ bool NVPTXLowerAggrCopies::runOnFunction(Function &F) {
         if (DL->getTypeStoreSize(load->getType()) < MaxAggrCopySize)
           continue;
 
-        User *use = *(load->use_begin());
+        User *use = load->user_back();
         if (StoreInst *store = dyn_cast<StoreInst>(use)) {
           if (store->getOperand(0) != load) //getValueOperand
             continue;
@@ -163,7 +163,7 @@ bool NVPTXLowerAggrCopies::runOnFunction(Function &F) {
   //
   for (unsigned i = 0, e = aggrLoads.size(); i != e; ++i) {
     LoadInst *load = aggrLoads[i];
-    StoreInst *store = dyn_cast<StoreInst>(*load->use_begin());
+    StoreInst *store = dyn_cast<StoreInst>(*load->user_begin());
     Value *srcAddr = load->getOperand(0);
     Value *dstAddr = store->getOperand(1);
     unsigned numLoads = DL->getTypeStoreSize(load->getType());
diff --git a/lib/Target/NVPTX/NVVMReflect.cpp b/lib/Target/NVPTX/NVVMReflect.cpp
index 5da8c2ed09..8b5444a66d 100644
--- a/lib/Target/NVPTX/NVVMReflect.cpp
+++ b/lib/Target/NVPTX/NVVMReflect.cpp
@@ -143,11 +143,9 @@ bool NVVMReflect::runOnModule(Module &M) {
   // ConstantArray can be found successfully, see if it can be
   // found in VarMap. If so, replace the uses of CallInst with the
   // value found in VarMap. If not, replace the use  with value 0.
-  for (Value::use_iterator I = ReflectFunction->use_begin(),
-                           E = ReflectFunction->use_end();
-       I != E; ++I) {
-    assert(isa<CallInst>(*I) && "Only a call instruction can use _reflect");
-    CallInst *Reflect = cast<CallInst>(*I);
+  for (User *U : ReflectFunction->users()) {
+    assert(isa<CallInst>(U) && "Only a call instruction can use _reflect");
+    CallInst *Reflect = cast<CallInst>(U);
 
     assert((Reflect->getNumOperands() == 2) &&
            "Only one operand expect for _reflect function");